The objective of our application is to develop hardware and procedures that will allow researchers to practically utilize phase plates in the back focal plane of the objective lens in a Transmission Electron Microscope. Use of precisely positioned phase plates can increase resolution in electron tomography, and also increase throughput when using the single-particle approach. Our specific aim is to provide a phase plate system that will include a modified objective aperture holder that incorporates (1) a piezo positioning system, (2) a heater to avoid contamination, and (3) an electrical feed-through for use with electrostatic phase plates. Simply exchanging the original objective aperture holder with the Hummingbird phase plate holder will allow nearly any cryo-EM to be equipped with a phase plate. The cost of this holder will be substantially lower than any other technology that can yield a similar improvement in imaging of frozen-hydrated specimens. In close collaboration with the Resource for the Visualization of Biological Complexity (RVBC) at the Wadsworth Center's NIH Biotechnological Resource, we will develop a new phase plate holder, demonstrate its use, and publish the results. It is our intent to develop and commercialize a cost effective system that will enable these techniques to become widely available to the biology research community. This proposal will develop tools that allow biologists to get a clearer picture of the structure and function of the cell. This knowledge is fundamental to innumerable areas of medical research and practice.